Tracheal tubes are used in conjunction with breathing problems to provide a better airway in the neck of a patient requiring assistance in breathing, as well as for conduction of anesthetic gas during a surgical operation. Tracheal tubes are of two general types, namely, tracheostomy tubes and endotracheal tubes.
A tracheostomy tube is inserted into the trachea of the patient through a surgically produced opening in the anterior neck. The shape of the tracheostomy tube is angled or L-shaped so that its upper end protrudes generally perpendicularly from the neck while its distal portion extends downwardly inside and parallel to the trachea. An endotracheal tube is inserted into the trachea through the mouth or nose, and is usually formed without a sharp bend but otherwise is substantially similar to the tracheostomy tube.
In a tracheal tube which is to serve as a conduit for anesthetic gas or to support breathing by providing a flow of oxygen or air from a respiration device, an inflatable balloon or cuff is ordinarily mounted adjacent the distal (inner) end of the tube. When the cuff is expanded by filling it with air, it presses against the tracheal wall thereby occluding the annular space between the tube and the wall. As a result, air flowing through the tube will fill the lungs without escaping back around the outside of the tube, because the cuff occludes that passage. Subsequent release of air pressure allows the lungs to exhale through the tube as in normal respiration.
Problems associated with present tracheal tubes detract from their utility, particularly where long term use of the tube is required or desirable, e.g., for more than seven days of intubation. One very significant problem is that they tend to cause abrasions and ulcerations; these result when the cuff and/or inner end of the tube rubs or scrapes against the tracheal wall. For example, in respiration each inhalation draws the trachea downwardly relative to the cuff, the trachea then returning upwardly in exhalation. In addition, the trachea increases and decreases in length as the tracheal rings move apart and come together. Normally, there may be about 18 such respirations a minute so that relative movement --and hence abrasion--is frequent. In addition, with each swallow the trachea moves upwardly (relative to the cuff) by elevation of the larynx; the trachea rapidly descends upon conclusion of the swallow. The swallowing movements occur at short intervals voluntarily or spontaneously to empty the pharynx of saliva, as well as during the ingestion of food. Such respiratory and swallowing movements, as well as sneezing, sighing and coughing, cause prior art tracheal tubes, which are fixed in place at their upper end and are of fixed length, to move up and down in relation to the trachea. This causes the inner end of the tube to scrape against the wall of the trachea, resulting in erosion of the posterior wall of the trachea and even of the adjacent esophagus. Movement of the inflatable cuff of the tube likewise results in rubbing and erosion of the mucosa of the trachea, causing abrasions and ulcerations to result. Ultimately scar tissue can build up, which can hinder breathing after tube removal.
The complications associated with prolonged intubation can be particularly severe. For example, chronic laryngotracheal stenoses can result, which may require a permanent tracheostomy, as well as tracheomalacia, the formation of fistulae between the trachea and the esophagus, and erosion of the anterior trachea and the innominate artery.